Reorientation and faulting of Pluto due to volatile loading within Sputnik Planitia

The location of Sputnik Planitia on Pluto is shown to result from volatiles sequestered within the basin forcing the reorientation of the dwarf planet, as supported by the planet-wide fault network. James Keane et al. report that the location of Sputnik Planitia, the approximately 1,000-kilometre-diameter topographic basin that dominates the surface of Pluto, is a natural consequence of the infill of volatile ices within the basin and the resulting reorientation (true polar wander) of the dwarf planet. As Sputnik Planitia slowly loaded with volatiles, the pull of tidal torques from Charon would have resulted in the eventual alignment of the basin with the Pluto–Charon tidal axis. Sputnik Planitia probably formed northwest of its present location, and was loaded with volatiles over million-year timescales as a result of volatile transport cycles. This is one of four papers on the geology of Sputnik Planitia in this issue of Nature. In News & Views, Amy Barr puts these latest contributions into context. Pluto is an astoundingly diverse, geologically dynamic world. The dominant feature is Sputnik Planitia—a tear-drop-shaped topographic depression approximately 1,000 kilometres in diameter possibly representing an ancient impact basin1,2. The interior of Sputnik Planitia is characterized by a smooth, craterless plain three to four kilometres beneath the surrounding rugged uplands, and represents the surface of a massive unit of actively convecting volatile ices (N2, CH4 and CO) several kilometres thick1,2,3,4,5. This large feature is very near the Pluto–Charon tidal axis. Here we report that the location of Sputnik Planitia is the natural consequence of the sequestration of volatile ices within the basin and the resulting reorientation (true polar wander) of Pluto. Loading of volatile ices within a basin the size of Sputnik Planitia can substantially alter Pluto’s inertia tensor, resulting in a reorientation of the dwarf planet of around 60 degrees with respect to the rotational and tidal axes. The combination of this reorientation, loading and global expansion due to the freezing of a possible subsurface ocean generates stresses within the planet’s lithosphere, resulting in a global network of extensional faults that closely replicate the observed fault networks on Pluto. Sputnik Planitia probably formed northwest of its present location, and was loaded with volatiles over million-year timescales as a result of volatile transport cycles on Pluto6,7. Pluto’s past, present and future orientation is controlled by feedbacks between volatile sublimation and condensation, changing insolation conditions and Pluto’s interior structure.